A Wiltshire Police call handler who is registered blind is cycling 250 miles in tandem from Land’s End to Bradford-on-Avon.
Anthony Bristowe who is from the Wiltshire town says his guide dog Nimmo is now reaching retirement.
Anthony wants to show his appreciation for the support he has received over the years from the Guide Dogs charity.
Anthony is completing the ride with cycling partner Simon Taylor.
Their marathon started at Land's End yesterday and a route is mapped out along quiet country lanes in Cornwall, Devon, Somerset and Wiltshire.
The pair arrive in Bradford-on-Avon on Saturday.
The tandem team will be joined by friends and some of Anthony’s police staff colleagues – including Chief Constable Mike Veale – to cycle the last 40 mile leg of the journey.
Anthony and Simon have set up a Just Giving page for anyone wishing to give a donation to help reach the £5,000 target they hope to raise for Guide Dogs.